Epidemiological study of risk factors from nursery and growing–finishing pig farms associated with rate ratio of pleuritis at slaughterhouse in the state of Santa Catarina, Brazil

This study aimed to identify risk factors related to management practices, environmental conditions, and infrastructure characteristics in nursery and growing-finishing pig farms located in the state of Santa Catarina, Brazil, and their association with the rate ratio of pleuritis at slaughter. A prospective observational study was conducted using a structured survey on 159 growing-finishing farms, totaling 162,252 slaughtered pigs, of which 5,126 (3.16%) carcasses showed macroscopic pleuritis lesions. Respiratory clinical signs were recorded for each monitored batch, and the characteristics of all nurseries and growing-finishing farms were evaluated. Macroscopic examination at slaughter was performed on all animals presenting pleuritis, assessing the type of exudate, lesion location, and extent, after carcasses were diverted for further inspection. A subsample of 697 pleural swabs and lung fragments was collected for molecular and histopathological analysis. A generalized regression model with a negative binomial distribution was used to estimate rate ratios and build a multivariate model using pleuritis cases as the outcome variable. Histopathological and molecular analyses revealed chronic lesions, and 11.5% of the samples tested positive for at least one pathogen. The findings suggest that pleuritis observed at slaughter likely originates during the early stages of production, when lesion severity may be underestimated and clinical signs overlooked. Moreover, management factors related to health practices, water quality, and the commingling of animals in nurseries and growing-finishing facilities were identified as key contributors to the occurrence and higher prevalence of pleuritis at slaughter.